Introduction
The camera functionality is a critical component of many Android applications, from simple photo-taking apps to sophisticated augmented reality experiences. Android developers have primarily two options when implementing camera capabilities: the lower-level Camera2 API and the newer, Jetpack-based CameraX library. This article explores both approaches, comparing their use cases, implementation complexities, and overall effectiveness.
Development History
Camera2 API
Introduced in Android 5.0 (Lollipop), the Camera2 API replaced the original Camera API, offering more fine-grained control over camera hardware. It was designed to provide access to advanced camera features and manual controls.
CameraX Library
CameraX is a Jetpack support library built on top of Camera2 API, released in 2019. It aims to simplify camera implementation while maintaining compatibility across most Android devices, addressing many of the challenges developers faced with Camera2.
Use Cases
When to Use Camera2 API
The Camera2 API is best suited for applications that require:
1. Advanced Camera Control: Access to manual focus, ISO, exposure time, and RAW image capture.
2. Custom Image Processing Pipelines: Building specialized image processing workflows.
3. Specific Hardware Feature Access: Leveraging device-specific camera capabilities.
4. Maximum Performance: When every millisecond of processing time matters.
5. Specialized Camera Applications: Professional photography apps, scientific imaging, or computer vision systems.
Example applications:
- Professional camera apps with manual controls
- Computational photography applications
- Specialized scientific or industrial imaging
- AR applications requiring precise camera control
When to Use CameraX Library
CameraX is ideal for:
1. Standard Camera Features: Taking photos, recording videos, image analysis, and preview.
2. Cross-Device Compatibility: When you need consistent behavior across different Android devices.
3. Rapid Development: When time-to-market is critical.
4. Integration with Lifecycle Components: Apps built with Android Jetpack architecture.
5. General-Purpose Camera Implementation: Social media, document scanning, or basic photo apps.
Example applications:
- Social media apps with photo/video capture
- Document scanning applications
- General-purpose camera apps
- Most standard consumer applications
Implementation Comparison
Camera2 API Implementation
Implementing Camera2 involves several complex steps:
1. Device Capability Check: Query `CameraManager` to get available cameras and their capabilities.
2. Create Camera Session: Open a `CameraDevice` and create a `CameraCaptureSession`.
3. Configure Surfaces: Set up `SurfaceView` or `TextureView` for preview.
4. Create Capture Requests: Configure and submit `CaptureRequest` objects.
5. Handle Callbacks: Implement multiple callback interfaces.
Here's a simplified code example of Camera2 implementation:
private void openCamera() {
CameraManager manager = (CameraManager) context.getSystemService(Context.CAMERA_SERVICE);
try {
String cameraId = manager.getCameraIdList()[0];
CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
// Check available capabilities
Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);
// Open camera device
manager.openCamera(cameraId, new CameraDevice.StateCallback() {
@Override
public void onOpened(@NonNull CameraDevice camera) {
cameraDevice = camera;
createCameraPreviewSession();
}
@Override
public void onDisconnected(@NonNull CameraDevice camera) {
camera.close();
cameraDevice = null;
}
@Override
public void onError(@NonNull CameraDevice camera, int error) {
camera.close();
cameraDevice = null;
}
}, backgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
private void createCameraPreviewSession() {
try {
SurfaceTexture texture = textureView.getSurfaceTexture();
texture.setDefaultBufferSize(previewSize.getWidth(), previewSize.getHeight());
Surface surface = new Surface(texture);
// Create request for preview
previewRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
previewRequestBuilder.addTarget(surface);
// Create capture session
cameraDevice.createCaptureSession(
Arrays.asList(surface, imageReader.getSurface()),
new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(@NonNull CameraCaptureSession session) {
if (cameraDevice == null) return;
cameraCaptureSession = session;
updatePreview();
}
@Override
public void onConfigureFailed(@NonNull CameraCaptureSession session) {
// Handle configuration failure
}
},
null
);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
CameraX Library Implementation
CameraX simplifies implementation with a more declarative approach:
1. Initialize the View: Set up `PreviewView` in the layout.
2. Define Use Cases: Configure `Preview`, `ImageCapture`, `VideoCapture`, or `ImageAnalysis`.
3. Bind to Lifecycle: Bind use cases to the activity/fragment lifecycle.
Here's a simplified code example of CameraX implementation:
private fun startCamera() {
val cameraProviderFuture = ProcessCameraProvider.getInstance(requireContext())
cameraProviderFuture.addListener({
val cameraProvider = cameraProviderFuture.get()
// Set up preview use case
val preview = Preview.Builder()
.build()
.also {
it.setSurfaceProvider(viewFinder.surfaceProvider)
}
// Set up image capture use case
val imageCapture = ImageCapture.Builder()
.setCaptureMode(ImageCapture.CAPTURE_MODE_MINIMIZE_LATENCY)
.build()
// Set up camera selector
val cameraSelector = CameraSelector.DEFAULT_BACK_CAMERA
try {
// Unbind any bound use cases before rebinding
cameraProvider.unbindAll()
// Bind use cases to camera
val camera = cameraProvider.bindToLifecycle(
this, cameraSelector, preview, imageCapture)
} catch(e: Exception) {
Log.e(TAG, "Use case binding failed", e)
}
}, ContextCompat.getMainExecutor(requireContext()))
}
private fun takePhoto() {
// Get a reference to the image capture use case
val imageCapture = imageCapture ?: return
// Create output file
val photoFile = File(outputDirectory, "photo_${System.currentTimeMillis()}.jpg")
// Create output options object
val outputOptions = ImageCapture.OutputFileOptions.Builder(photoFile).build()
// Set up image capture listener
imageCapture.takePicture(
outputOptions,
ContextCompat.getMainExecutor(requireContext()),
object : ImageCapture.OnImageSavedCallback {
override fun onImageSaved(output: ImageCapture.OutputFileResults) {
// Handle successful image capture
}
override fun onError(exc: ImageCaptureException) {
// Handle error
}
}
)
}
```
Effectiveness Comparison
Learning Curve and Development Speed
Camera2 API:
- Steep learning curve
- Requires thorough understanding of camera pipeline
- Lengthy implementation time
- Significant boilerplate code
- Error-prone for beginners
CameraX Library:
- Gentle learning curve
- Intuitive API design
- Rapid implementation
- Minimal boilerplate
- Developer-friendly abstractions
Cross-Device Compatibility
Camera2 API:
- Inconsistent behavior across manufacturers
- Requires extensive device-specific testing
- May need fallback implementations
- More sensitive to hardware variations
CameraX Library:
- Built-in device compatibility layer
- Consistent behavior across devices
- Vendor extensions for device-specific features
- Built-in testing across thousands of devices
Performance
Camera2 API:
- Lower-level access may offer better performance
- Finer control over memory usage
- Can optimize for specific hardware
- Better for specialized real-time processing
CameraX Library:
- Slight overhead due to abstraction layer
- Optimized for common use cases
- Performance differences negligible for most applications
- Background thread management handled automatically
Maintenance
Camera2 API:
- More prone to breaking with OS updates
- Requires more frequent updates
- Higher maintenance burden
- More custom code to maintain
CameraX Library:
- Part of Jetpack, receives regular updates
- Forward compatibility focus
- Lower maintenance overhead
- Bugs fixed as part of library updates
Code Size Comparison
A typical implementation of basic camera functionality (preview, photo capture, and flash control):
Camera2 API: ~800-1200 lines of code
CameraX Library: ~150-300 lines of code
Integration with Modern Android Architecture
Camera2 API
- Requires custom integration with lifecycles
- Manual management of threading
- Custom error handling implementation
- No built-in ML Kit integration
CameraX Library
- Lifecycle-aware by design
- Coroutines support
- Extension integration (e.g., HDR, bokeh)
- Seamless ML Kit integration for image analysis
Conclusion
When to Choose Camera2 API
Choose Camera2 API when:
- You need maximum control over camera hardware
- Your application requires access to specialized camera features
- Performance optimization at the hardware level is critical
- You're building professional camera applications
- You require very specific custom image processing
When to Choose CameraX Library
Choose CameraX when:
- You want faster development time
- Cross-device compatibility is essential
- You're using Jetpack components
- Your camera requirements are standard
- You want reduced maintenance overhead
In most scenarios, CameraX provides the best balance of functionality, ease of use, and compatibility for modern Android applications. However, Camera2 API remains valuable for specialized use cases where granular control is necessary.
CameraX encapsulates the complexities of Camera2 while providing a consistent experience across devices—making it the recommended choice for most Android developers implementing camera functionality today.
References
1. Android Developers Documentation: [Camera2 API](https://developer.android.com/reference/android/hardware/camera2/package-summary)
2. Android Developers Documentation: [CameraX](https://developer.android.com/training/camerax)
3. Google Codelabs: [Getting Started with CameraX](https://codelabs.developers.google.com/codelabs/camerax-getting-started)